what is a campaign contribution?

why do interest groups choose this as a technique to their advantage.

this is what i have: Campaign contributions is getting financial help from resources or buying support from candidates.
getting support helps the groups to also get publicity and money to have more ads.

i don't know if this is right. can you help me expand on it

Essentially, you're right.

A campaign contribution is money given to help a particular candidate (or party) get elected. Individuals and interest groups give campaign contributions.

Interest groups pay this money in hopes that their candidates get elected and will help them achieve their agendas.