add start of glossary (#1946)

This is the start of a glossary in the docs for terms that folks might not know when first learning Slate. Hopefully it makes it easier to learn. If anyone wants to help fill it out, that would be amazing. Thanks!

docs/Readme.md

@@ -25,6 +25,7 @@
 * [Contributing](../Contributing.md)
 * [Changelog](./general/changelog.md)
 * [FAQ](./general/faq.md)
+* [Glossary](./general/glossary.md)
 
 ## Slate Core
 

docs/general/glossary.md

@@ -0,0 +1,101 @@
+# Glossary
+
+A glossary explaining the terms commonly used in Slate:
+
+### Anchor
+
+### Block
+
+### Blur
+
+### Change
+
+### Character
+
+A "character" is the smallest element that makes up a text node in Slate.
+
+### Collapsed
+
+### Core
+
+### Data
+
+### Decoration
+
+### Document
+
+The "document" is the top-level ["node"](#node) that contains all other nodes that make up the content of the Slate editor.
+
+### Editor
+
+### Extend
+
+### Focus
+
+### Fragment
+
+### History
+
+### Inline
+
+### Key
+
+Keys are unique identifiers given to nodes in Slate to be able to reference them uniquely even as the document changes.
+
+### Mark
+
+### Merge
+
+### Model
+
+### Node
+
+### Normalize
+
+### Offset
+
+An offset is a distance from the start of a text node, measured in ["characters"](#character).
+
+### Operation
+
+### Placeholder
+
+### Plugin
+
+### Point
+
+A point represents a specific location in a document, where a user's cursor could be placed. It is represented by the `key` of the node in the document, and the `offset` of characters into a node.
+
+### Range
+
+A range is a way to represent a specific section of a document between two ["points"](#point). It is modelled after the [DOM Range](https://developer.mozilla.org/en-US/docs/Web/API/Range) concept.
+
+### Redo
+
+### Rule
+
+### Schema
+
+### Selection
+
+### Serializer
+
+### Split
+
+### Stack
+
+### Text
+
+### Undo
+
+### Unwrap
+
+To "unwrap" is the opposite of to ["wrap"](#wrap), removing a surrounding node from a selection.
+
+### Validate
+
+### Value
+
+### Wrap
+
+To "wrap" is to surround a piece of text or a node in another node. For example, if you select the text `Google` and want to turn it into a link, you'd "wrap" it with an inline link node.