It's natural to be curious about your body and changes during puberty. Masturbation is when a person touches their own genitals for pleasure and may lead to ejaculation, which is the release of semen. This is a normal and healthy part of growing up for many males.
Your mom probably gave you tissues to help you stay clean when you masturbate. Since ejaculation can produce some fluid, tissues are useful to gently clean yourself afterward and help maintain good hygiene.
Remember, masturbation is a private activity that people usually do in a private space. It's important to respect privacy and understand your body. If you have more questions or feel unsure about anything, consider talking to a trusted adult, like a parent, school counselor, or healthcare provider.