Lexical normalization is the task of translating/transforming a non standard text to a standard register.

Example:

new pix comming tomoroe
new pictures coming tomorrow

Datasets usually consists of tweets, since these naturally contain a fair amount of these phenomena.

For lexical normalization, only replacements on the word-level are annotated. Some corpora include annotation for 1-N and N-1 replacements. However, word insertion/deletion and reordering is not part of the task.