'Can' is always used as principal verb, and never used as auxillary verb, and its object is infinitive. It is used--
a. To denote strength, ability, power or authority.
b. To denote permission.
c. In asking question.
a. I can carry a bundle (strength).
I can dismiss you (power).
He can solve this sum (ability).
b. You can take it.
c. Can you come tomorrow?