Even new no-limit hold'em players tend to learn early on that most of the time — and for a variety of reasons — it is better to open with a raise than to limp before the flop.
Like everything in poker, this isn't a hard-and-fast rule with no exceptions. Sometimes circumstances make limping a viable option, including in multi-way pots where it appears you can limp in after others and see a flop cheaply with great pot odds.
But if it folds to you and you are opening the action, limping generally works as an invitation to others to raise after you.