Modern English has six tenses, each of which has a corresponding continuous tense.
The first three tenses, present, past, and future, present few problems. Only third person singular in the present tense differs in form:
Present tense of regular (weak) verbs:
Today I walk. Today he walks.
Yesterday I walked.
Tomorrow I shall/will walk.
The dwindling class of irregular (strong) verbs must be learned individually.
Today I go. Today he goes.
Yesterday I went.
Tomorrow I shall/will go.
The other three tenses, perfect, pluperfect, and future perfect, are formed with the helping verbs have, has, and had.
perfect: used to express an event that has just finished, and to describe an event which, although in the past, has effects that continue into the present.
Queen Elizabeth has reigned for 56 years.
pluperfect (past perfect): used to express an event that took place before another action, also in the past.
I had driven all the way to Oklahoma when I realized my mistake.
future perfect: used to express an event that will have taken place at some time in the future.
As of February 26, I shall have been in this job six years.
For complete conjugation tables of weak and strong English verbs, see the Wikipedia article.