They are all forms of the verb to do. The verb to do can be used as an action verb and also as an auxiliary verb.In some cases, to do is used as a verb that expresses an action. It is also common to use do, does and did as auxiliary verbs (or helping verbs) together with another verb in its base form. This is used to create negative sentences, questions, or for adding emphasis.
Example :
1. Shankar always does his taxes on time.
2. Volunteers do a lot of work around the town.
3. Raman did a great job on his history report for school.
4. You have done nothing all morning!
5. I am doing the best I can!