Consent is key in any form of sexual activity. We should all be able to make choices about what we want, or don't want, to do with our bodies.
If you are forced or coerced into doing something against your will, you have not given consent. You may not be able to give consent if you are under the influence of alcohol or drugs or if you cannot communicate easily because of a disability. Regardless of what the act or activity is, if you have not given consent you have been the victim of sexual violence, assault or abuse. The section called What is Sexual Violence and Abuse gives more information.
The Consent Coalition is a charity in Nottingham who have designed a set of resources to help people understand what consent is in various contexts. These resources are free to download and you can find them on the Consent Coalition website.