Map type and map function.

Data type description template also added.

docs/_description_templates/template-data-type.md

@@ -0,0 +1,29 @@
+---
+toc_priority: 
+toc_title: 
+---
+
+# data_type_name {#data_type-name}
+
+Description.
+
+**Parameters** (Optional)
+
+-   `x` — Description. [Type name](relative/path/to/type/dscr.md#type).
+-   `y` — Description. [Type name](relative/path/to/type/dscr.md#type).
+
+**Examples**
+
+```sql
+
+```
+
+## Additional Info {#additional-info} (Optional)
+
+The name of an additional section can be any, for example, **Usage**.
+
+**See Also** (Optional)
+
+-   [link](#)
+
+[Original article](https://clickhouse.tech/docs/en/data_types/<data-type-name>/) <!--hide-->

docs/en/sql-reference/data-types/map.md

@@ -0,0 +1,56 @@
+---
+toc_priority: 65
+toc_title: Map(key, value)
+---
+
+# Map(key, value) {#data_type-map}
+
+`Map(key, value)` data type stores `key:value` pairs in structures like JSON. 
+
+**Parameters** 
+-   `key` — Key part of the pair. [String](../../sql-reference/data-types/string.md) or [Integer](../../sql-reference/data-types/int-uint.md).
+-   `value` — Value part of the pair. [String](../../sql-reference/data-types/string.md), [Integer](../../sql-reference/data-types/int-uint.md) or [Array](../../sql-reference/data-types/array.md).
+
+!!! warning "Warning"
+    Currently `Map` data type is an experimental feature. To work with it you must set `allow_experimental_map_type = 1`.
+
+To get the value from an `a Map('key', 'value')` column, use `a['key']` syntax.
+
+**Example**
+
+Query:
+
+``` sql
+CREATE TABLE table_map (a Map(String, UInt64)) ENGINE=Memory;
+INSERT INTO table_map VALUES ({'key1':1, 'key2':100}), ({'key1':2,'key2':200}), ({'key1':3,'key2':300});
+SELECT a['key2'] FROM table_map;
+```
+Result:
+
+```text
+┌─arrayElement(a, 'key2')─┐
+│                     100 │
+│                     200 │
+│                     300 │
+└─────────────────────────┘
+```
+
+## Map() and Tuple() Types {#map-and-tuple}
+
+You can cast `Tuple()` as `Map()`:
+
+``` sql
+SELECT CAST(([1, 2, 3], ['Ready', 'Steady', 'Go']), 'Map(UInt8, String)') AS map;
+```
+
+``` text
+┌─map───────────────────────────┐
+│ {1:'Ready',2:'Steady',3:'Go'} │
+└───────────────────────────────┘
+```
+
+**See Also**
+
+-   [map()](../../sql-reference/functions/tuple-map-functions.md#function-map) function
+
+[Original article](https://clickhouse.tech/docs/en/data_types/map/) <!--hide-->

docs/en/sql-reference/functions/tuple-map-functions.md

@@ -5,6 +5,68 @@ toc_title: Working with maps
 
 # Functions for maps {#functions-for-working-with-tuple-maps}
 
+## map {#function-map}
+
+Arranges `key:value` pairs into a JSON data structure.
+
+**Syntax** 
+
+``` sql
+map(key1, value1[, key2, value2, ...])
+```
+
+**Parameters** 
+
+-   `key` — Key part of the pair. [String](../../sql-reference/data-types/string.md) or [Integer](../../sql-reference/data-types/int-uint.md).
+-   `value` — Value part of the pair. [String](../../sql-reference/data-types/string.md), [Integer](../../sql-reference/data-types/int-uint.md) or [Array](../../sql-reference/data-types/array.md).
+
+**Returned value**
+
+-   JSON with `key:value` pairs.
+
+Type: [Map(key, value)](../../sql-reference/data-types/map.md).
+
+**Examples**
+
+Query:
+
+``` sql
+SELECT map('key1', number, 'key2', number * 2) FROM numbers(3);
+```
+
+Result:
+
+``` text
+┌─map('key1', number, 'key2', multiply(number, 2))─┐
+│ {'key1':0,'key2':0}                              │
+│ {'key1':1,'key2':2}                              │
+│ {'key1':2,'key2':4}                              │
+└──────────────────────────────────────────────────┘
+```
+
+Query:
+
+``` sql
+CREATE TABLE table_map (a Map(String, UInt64)) ENGINE = MergeTree() ORDER BY a;
+INSERT INTO table_map SELECT map('key1', number, 'key2', number * 2) FROM numbers(3);
+SELECT a['key2'] FROM table_map;
+```
+
+Result:
+
+``` text
+┌─arrayElement(a, 'key2')─┐
+│                       0 │
+│                       2 │
+│                       4 │
+└─────────────────────────┘
+```
+
+**See Also** 
+
+-   [Map(key, value)](../../sql-reference/data-types/map.md) data type
+
+
 ## mapAdd {#function-mapadd}
 
 Collect all the keys and sum corresponding values.
@@ -112,4 +174,4 @@ Result:
 └──────────────────────────────┴───────────────────────────────────┘
 ```
 
-[Original article](https://clickhouse.tech/docs/en/query_language/functions/tuple-map-functions/) <!--hide-->
+[Original article](https://clickhouse.tech/docs/en/sql-reference/functions/tuple-map-functions/) <!--hide-->