These "easy words" that help you start sentences are also called "transition words," and their job is to link ideas together. You can use them in starting an essay or in any sentence in a paper; however, they are most effective when used inside the text, and particularly so as the first word in a paragraph. These transition words can help you to show that you are:
1. Adding an additional example or reason (moreover, additionally, furthermore, not only...but also).
2. Presenting a contrasting idea (however, on the other hand, in contrast, on the one hand...on the other hand).
3. Explaining the order of things (first...second...third, next, afterward, finally).