People keep telling me I need to be saved, and I nod along without really knowing what they mean. Can someone explain it plainly?

“But he was wounded for our transgressions, he was bruised for our iniquities: the chastisement of our peace was upon him; and with his stripes we are healed. All we like sheep have gone astray; we have turned every one to his own way; and the LORD hath laid on him the iniquity of us all.”

Isaiah wrote centuries before Jesus, describing a servant who suffers on behalf of others while those others wander off like sheep. Israel read it as a puzzle it could never quite solve. The early church read it and recognized Jesus. For anyone trying to work out what being saved means, this is the shape of it: someone else absorbing what you could not carry, deliberately, in your place.

“For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures:”

Paul is quoting a summary that was already old when he wrote it, passed around by people who had been there. It is deliberately short: Christ died for our sins, was buried, and rose again. That is the whole message before any theology gets built on top of it. If you want the plain version of Christianity, this is it, and it is small enough to hold in your head.