Did is a past form of "Do."
Do- 1. Perform (an action, the precise nature of which is often unspecified).
2. Achieve or complete, in particular:
3. Act or behave in a specified way.
4. Be suitable or acceptable.
5. Used before a verb (except be, can, may, ought, shall, will ) in questions and negative statements.
6. Used to refer back to a verb already mentioned.
7. Used to give emphasis to a positive verb.
8. Used with inversion of a subject and verb when an adverbial phrase begins a clause for emphasis.
Poonam did all the tasks.