When do you use the gerund?

The gerund is the present continuous tense, and is used to describe things that you are doing. It is commonly translated with the ending -ing in English. For example, 'I am eating an apple', "estoy comiendo una manzana", as opposed to 'I eat an apple', "como una manzana". It implies a more continuous action than the present tense, something that is happening right now.