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 dieresis, le tréma, is a French accent found only on two vowels: ë and ï. The dieresis 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.
When the letters o and e are pronounced as a single sound, they combine into a symbol called a ligature: œ. The pronunciation of this symbol depends on the letter(s) that follow it.