Vim / Neovim enables us to manipulate text in various ways, in which, for example, we can sort lines or make them unique. Here are the examples.

Sort

Use sort command.
Besides, here is the documentation of Vim / Neovim.

Specify sort order

1. ASC

By default.

:%sort

2. DESC

Append !.

:%sort!

3. Numeric sort

Give n as a parameter.

:%sort n

Specify sort range

1. Whole text

Use % as usual.

:%sort

2. Specific lines only

Add startNum,endNum to the head.
2-5 lines only, for example:

:2,5sort

3. Visual selection

As is.

:'<, '>sort

An example of order + range (combination)

Here is a DESC + numeric sort example.

:%sort! n

Make lines unique

Use sort command as well. Give it u as a parameter.

:%sort u