Je voudrais vs je veux to say that you want something in French

Look at these examples:

Note that to ask for something in French, you could use two forms of the verb vouloir: 
je veux (I want) or je voudrais (I would want/like)

Je voudrais is preferable in social contexts such as in a restaurant, as it is more polite and subtle than the blunt je veux (just like in English).

[Note that j'aimerais (I would like) is also very commonly used in more polite contexts.]

Grammar point: Je veux is in Le Présent tense (I want), whereas je voudrais is in Le Conditionnel (I would want/like).