It is a slightly more informal way to say "Can you do this?" or "Are you able to do this?" It implies that the speaker wants a definite answer, either yes or no.
Here are some examples of how you might use this phrase:
* ¿Si puedes o no limpiar la cocina? (Can you clean the kitchen or not?)
* ¿Si puedes o no venir a mi fiesta? (Can you come to my party or not?)
* ¿Si puedes o no ayudarme con esto? (Can you help me with this or not?)
The phrase "si puedes o no" emphasizes the desire for a clear answer, indicating that the speaker is waiting for a response and wants to know if the other person is capable of doing what is being asked.