fix: applied suggestions from code review

pages/book/cells.mdx

@@ -2,11 +2,11 @@
 
 import { Callout } from 'nextra/components'
 
-[Cells](#cells), [Builders](#builders) and [Slices](#slices) are low-level [primitives][p] of TON Blockchain. The virtual machine of TON Blockchain, [TVM][tvm], uses cells to represent all data structures in memory and persistent storage.
+[Cells](#cells), [Builders](#builders) and [Slices](#slices) are low-level [primitives][p] of TON Blockchain. The virtual machine of TON Blockchain, [TVM][tvm], uses cells to represent all data structures in persistent storage, and most in memory.
 
 ## Cells
 
-`Cell{:tact}` is a [primitive][p] and a data structure, which [ordinarly](#cells-kinds) consists of up to $1023$ continuously laid out bits and up to $4$ references to other cells. Circular references are forbidden and cannot be created by the means of [TVM][tvm], which means cells can be viewed as [quadtrees][quadtree] or [directed acyclic graphs (DAGs)](https://en.wikipedia.org/wiki/Directed_acyclic_graph) of themselves. [TVM][tvm] code itself is represented by a tree of cells.
+`Cell{:tact}` is a [primitive][p] and a data structure, which [ordinarly](#cells-kinds) consists of up to $1023$ continuously laid out bits and up to $4$ references to other cells. Circular references are forbidden and cannot be created by the means of [TVM][tvm], which means cells can be viewed as [quadtrees][quadtree] or [directed acyclic graphs (DAGs)](https://en.wikipedia.org/wiki/Directed_acyclic_graph) of themselves. Contract code itself is represented by a tree of cells.
 
 Cells and [cell primitives](#cells-immutability) are bit-oriented, not byte-oriented: [TVM][tvm] regards data kept in cells as sequences (strings or streams) of up to $1023$ bits, not bytes. If necessary, contracts are free to use, say, $21$-bit integer fields serialized into [TVM][tvm] cells, thus using fewer persistent storage bytes to represent the same data.
 

pages/book/types.mdx

@@ -16,10 +16,12 @@ Tact supports a number of primitive data types that are tailored for smart contr
 * [`Int{:tact}`](/book/integers) — all numbers in Tact are $257$-bit signed integers, but [smaller representations](/book/integers#serialization) can be used to reduce storage costs.
 * [`Bool{:tact}`](#booleans) — classical boolean with `true{:tact}` and `false{:tact}` values.
 * `Address{:tact}` — standard [smart contract address](https://docs.ton.org/learn/overviews/addresses#address-of-smart-contract) in TON Blockchain.
-* [`Cell{:tact}`](/book/cells#cells), [`Builder{:tact}`](/book/cells#builders), [`Slice{:tact}`](/book/cells#slices) — low-level primitives of TON VM.
-* `String{:tact}` — represents text strings in TON VM.
+* [`Cell{:tact}`](/book/cells#cells), [`Builder{:tact}`](/book/cells#builders), [`Slice{:tact}`](/book/cells#slices) — low-level primitives of [TVM][tvm].
+* `String{:tact}` — immutable text strings.
 * `StringBuilder{:tact}` — helper type that allows you to concatenate strings in a gas-efficient way.
 
+[tvm]: https://docs.ton.org/learn/tvm-instructions/tvm-overview
+
 ### Booleans [#booleans]
 
 The primitive type `Bool{:tact}` is the classical boolean type, which can hold only the two values: `true{:tact}` and `false{:tact}`. It's convenient for boolean and logical operations, as well as for storing flags.

pages/ref/core-cells.mdx

@@ -89,7 +89,7 @@ extends fun hash(self: Cell): Int;
 
 Extension function for the [`Cell{:tact}`][cell].
 
-Calculates and returns a hash of the [`Cell{:tact}`][cell] as an [`Int{:tact}`][int].
+Calculates and returns an [`Int{:tact}`][int] value of the [SHA-256][sha-2] hash of the [standard `Cell{:tact}` representation][std-repr] of the given [`Cell{:tact}`][cell].
 
 Usage example:
 
@@ -214,7 +214,7 @@ extends fun storeCoins(self: Builder, value: Int): Builder;
 
 Extension function for the [`Builder{:tact}`][builder].
 
-Stores (serializes) an unsigned [`Int{:tact}`][int] `value` in the range $0 .. 2^{120} − 1$ into the copy of the [`Builder{:tact}`][builder]. The serialization of `value` consists of a $4$-bit unsigned big-endian integer $l$, which is the smallest integer $l ≥ 0$, such that `value` $< 2^{8 * l}$, followed by an $8 * l$-bit unsigned big-endian representation of `value`. If `value` does not belong to the supported range, a range check exception is thrown. Returns that copy of the [`Builder{:tact}`][builder].
+Stores (serializes) an unsigned [`Int{:tact}`][int] `value` in the range $0 .. 2^{120} − 1$ into the copy of the [`Builder{:tact}`][builder]. The serialization of `value` consists of a $4$-bit unsigned big-endian integer $l$, which is the smallest integer $l ≥ 0$, such that `value` $< 2^{8 * l}$, followed by an $8 * l$-bit unsigned big-endian representation of `value`. Returns that copy of the [`Builder{:tact}`][builder].
 
 Attempts to store an out-of-bounds `value` throw an exception with [exit code 5](/book/exit-codes#5): `Integer out of expected range`.
 
@@ -710,7 +710,7 @@ extends fun hash(self: Slice): Int;
 
 Extension function for the [`Slice{:tact}`][slice].
 
-Calculates and returns a hash of the [`Slice{:tact}`][slice] as an [`Int{:tact}`][int].
+Calculates and returns an [`Int{:tact}`][int] value of the [SHA-256][sha-2] hash of the [standard `Cell{:tact}` representation][std-repr] of the given [`Slice{:tact}`][slice].
 
 Usage example:
 
@@ -960,4 +960,7 @@ fun cautiousParse(payload: Slice): TripleAxe? {
 [struct]: /book/structs-and-messages#structs
 [message]: /book/structs-and-messages#messages
 
+[std-repr]: /book/cells#cells-representation
+
 [tlb]: https://docs.ton.org/develop/data-formats/tl-b-language
+[sha-2]: https://en.wikipedia.org/wiki/SHA-2#Hash_standard