Update terminology to be modern

Author: SirJosh3917

design/witx-type-representation.md

@@ -14,49 +14,9 @@ found here](https://github.com/WebAssembly/interface-types/blob/master/proposals
 The endian-ness of these types are **little endian**, as _all_ types in the WebAssembly
 type system are little endian. [See here for more information](https://github.com/WebAssembly/design/issues/786#issuecomment-244548105).
 
-# Enum(T)
+# Record
 
-An `Enum(T)` is simply is a `T`. However, the value of T can only be one of the
-specific variants of the enum. This type lends itself to describing when
-something can only be one of the enumerations in the group (for example, in a
-group of Dogs and Cats, you may have an enum representing either a Dog or a
-Cat).
-
-```
-errno: Enum(u32)
-+------+------+------+------+
-| 0x00 | 0x00 | 0x00 | 0x15 |
-+------+------+------+------+
-^ fault
-```
-
-(`clockid` despite only representing 4 values is an `Enum(u32)`. This is
-primarily for ABI compatibility, and future-proofing.)
-
-# Flags(T)
-
-A `Flags(T)` datatype takes up exactly a `T` in memory, similar to `Enum(T)`.
-However, each variant of a `Flags(T)` will take up exactly one bit in the data.
-This allows the usage of bitwise AND, bitwise OR, and bitwise NOT operators to
-combine, check, or exclude specific values in the flag very easily. This type
-lends itself to describing capabilities.
-
-```
-oflags: Flags(u16)
-
-+-----------------+-----------------+
-| 0 1 1 0 0 0 0 0 | 0 0 0 0 0 0 0 0 |
-+-----------------+-----------------+
-  ^ ^ ^ ^
-  | | | trunc
-  | | excl
-  | directory
-  creat
-```
-
-# Struct
-
-A `Struct` is a type that takes up some contiguous amount of memory, with each
+A `Record` is a type that takes up some contiguous amount of memory, with each
 field taking up a specific amount of reserved bytes. Interpreting the bytes as
 one of the types in Witx will yield a usable value.
 
@@ -72,26 +32,36 @@ buf_len: size @ offset 4
 ^buf                        ^buf_len
 ```
 
-The `Size` of a `Struct` refers to how many contiguous bytes it takes up in
+The `Size` of a `Record` refers to how many contiguous bytes it takes up in
 memory.
 
-The `Alignment` of a `Struct` refers to <X>.
+The `Alignment` of a `Record` refers to the byte boundary that the record must
+be on in memory. For example, the above `iovec` could only ever get allocated
+to a memory address that is divisible by 4, because the alignment is 4.
 
-# Union
+# Variant
 
-A `Union` is a type which uses `tag_size` bytes to determine which variant of
-the union the data will be. The data is simply inserted as is with whatever
+A `Variant` is a type which uses some bits to determine which variant of
+the variant the data will be. The data is simply inserted as is with whatever
 type it may be.
 
+```
+errno: Variant
++------+------+------+------+
+| 0x00 | 0x00 | 0x00 | 0x15 |
++------+------+------+------+
+^ fault
+```
+
 ```
 subscription_u
 
 +------+------+------+------+------+------+------+------+
 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 |
 +------+------+------+------+------+------+------+------+
-^ padding due to the alignment of the union      ^tag_size
+^ padding due to the alignment of the variant    ^tag_size
 
-cont. 32 bytes for the union's data
+cont. 32 bytes for the variant's data
 +------+------+------+------+------+------+------+------+
 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 |
 +------+------+------+------+------+------+------+------+
@@ -101,9 +71,9 @@ cont. 32 bytes for the union's data
 +------+------+------+------+------+------+------+------+
 ```
 
-# Pointer<T> and Array<T>
+# Pointer<T> and List<T>
 
-A `Pointer<T>` and `Array<T>` are both just `Pointer<T>`s. A `Pointer<T>`'s
+A `Pointer<T>` and `List<T>` are both just `Pointer<T>`s. A `Pointer<T>`'s
 size is guaranteed to be 8 bytes, but if on a 32 bit architecture it will only
 use 4 of the 8 bytes. The pointers themselves are 32 bit, as wasm32 is the only
 ABI currently implemented. In the future when the specification for wasm64 is