A clause is a part of a sentence. Some sentences have two or more clauses:

•  Jim hurt his arm playing tennis.

Playing tennis - ing clause
Jim hurt himself - main clause

•  Feeling tired, I went to bed early.

Feeling tired - ing clause
I went to bed early - main clause

"Playing tennis" and "feeling tired" are -ing clauses.

If the -ing clause is first (as in the second example), we write a comma (,) between the clauses.

When two things happen at the same time, you can use -ing for one of the verbs. The main clause
usually comes first:

•  I've just seen Carol. She's in the bar having a drink. (= she is in the bar and she is having
a drink)
•  A man ran out of the house shouting. (= he ran out of the house and he was shouting)
•  Do something! Don't just stand there doing nothing!

We also use -ing when one action happens during another action. We use -ing for the longer
action. The longer action is the second part of the sentence:

•  Jim hurt his arm playing tennis. (= while he was playing)

•  Did you cut yourself shaving? (= while you were shaving)
You can also use -ing after while or when:

•  Jim hurt his arm while playing tennis.
•  Be careful when crossing the road. (= when you are crossing)

When one action happens before another action, we use having (done) for the first action:

•  Having found a hotel, we looked for somewhere to have dinner.

•  Having finished her work, she went home.
You can also say after -ing:

•  After finishing her work, she went home.

If one short action follows another short action, you can use the simple -ing form (doing instead
of having done) for the first action:

•  Taking a key out of his pocket, he opened the door.

These structures are used more in written English than in spoken English.

You can use an -ing clause to explain something or to say why somebody does something. The
-ing clause usually comes first:

•  Having already seen the film twice, I didn't want to go to the cinema. (= because I had
already seen it twice)
•  Feeling tired, I went to bed early. (= because I felt tired)
•  Being unemployed, he hasn't got much money. (= because he is unemployed)
•  Not having a car, she finds it difficult to get around. (= because she doesn't have a car)

These structures are used more in written English than in spoken English.