A date is any activity that you and your love-interest go to, to have fun of course, with the main objective of the two people or more [can be a double date or something] getting to know each other more.
Let's put it this way, if she likes you and you ask her for her phone number in the beginning and gives it to you, that's the best sign she is interested in you. If a girl likes you mutually as much as you like her, she'll be sort of thinking the way you're thinking; with you always on their mind as well

. Also, if you want to make it an official date, just ask her! If she likes you she'll respond with "sure let's go" or something similar to that, if she denies you or replies with a "date? what do you mean by that?" or something similar to that response, then you know that she's clearly not as interested as you expected. Look for signs
GUYS! Don't ever land in the friend zone right off the bat if you're interested in a girl. Be yourself. If you're interested in becoming b/f material, don't hesitate to ask her out; otherwise, you're going to be her best guy girlfriend instead. Then obviously you'll regret it.