Before looking at Irregular Verbs lets look at Regular Verbs.
In English, regular verbs in the Past Simple Tense and the Past Participle are formed by:
adding +ed or +d to the base form of the verb
Verbs that have a different form are considered Irregular Verbs.
English has hundreds of irregular verbs.
Common Irregular Verbs List
When a verb is irregular, other forms of the verb stem with prefixes or suffixes, will also be irregular:
do – done – did
undo – undone – undid
redo – redone – redid