Answer:
Front loading is a practice to hold primaries and caucuses earlier than the season usually starts. Historically, Iowa and New Hampshire used to do their primaries or caucuses first, which gave significance to the result candidates would have in these states. As a result, a number other states started to adopt the same practice, which became known as front-loading.
This practice poses a danger to the candidates, because it is more favorable to candidates with strong funding and prior formed support based, while new candidates who need to fund raise and run grass-root campaigns simply have less time to do so, which jeopardizes their chances.