There are four basic ways to describe what's going on in your cocktail:
Strong: refers to the main alcohol in your drink. That's your vodka, gin, or whatever your preferred liqour might be.
Weak: refers to the lesser alcohol part of your drink. This might be a liqueur (St. Germain for example) or fortified wines.
Sour: Means that there's a citrus note — lemon, lime, or orange.
Sweet: This one's pretty obvious, but that means there's sugar or syrup involved.