Fractions, decimals and percents are basically the same thing except they have different names and are expressed differently. For example 1/2 .5 and 50% are the same thing.
Fractions tell you how much that you have of that number. So if I took a pie and split it into 6 pieces and I had a piece in my hand I would have 1/6 of the pie in my hand. For decimals the 1 in .1 would be the tenths place, if you added a zero it would be the hundredths place and if you added another the thousandths place and so on and so forth. For Multiplying fractions you would just times the top number and the bottom number. For example 1/2 time 1/3 would be 1/5. But why would it be smaller than the number you started with? Because when you take a halve of a third you have to find a denominator and take from it then you would get a Fifth. It is easier if you use a clock.