 Our second example sentence, I am playing football at the moment, is the present continuous tense. This has a different structure. It has the subject, I, the verb to be in the present tense, am, is, or are, plus the verb with an I in G on the end. So here I am playing football at the moment. Whereas the present simple tense is used to talk about habits, routines and facts, the present continuous tense is used to talk about actions in progress at the time of speaking or around the time of speaking. Our third example sentence is the present perfect. I have played football twice this week. Here the structure is the subject, I, auxiliary verb have or has, plus the past participle. The past participle is usually formed just by adding ED on to the end of the base form of the verb. However, students need to be aware of the many irregular verbs such as no would change to known, go, to gone, understand, to understood and so on. Unfortunately there are no rules for this and they just have to be learnt individually.