While French has the same alphabet as English, some of the letters have little decorations that can make them look and sound very different. In French, accents are essential: they're there for a reason, so you must include them when writing.
In French, E is the only letter that can be modified with l'accent aigu, the acute accent. With the accent, it may be called either e accent aigu or simply é, pronounced [e]. As indicated by the latter, the acute accent changes the vowel's pronunciation to [e].
The little hook added under the letter c in French is a diacritical mark known as a cedilla, une cédille: ç. The letter c with the hook is called c cédille.
The circumflex, aka "little hat," is the only French accent that may be found on any of the five vowels. In any given word, the circumflex may serve one or more purposes.
The dieresis, le tréma, is a French accent found only on three vowels: ë, ï, and ü. The dieresis usually indicates that the accented vowel must be pronounced distinctly from the vowel that precedes it.
Only three French vowels can take the grave accent: à, è, and ù, and the purpose of the accent depends on the letter in question.