Here you go. Calling each number in the data-set a "term"

mode is the term that occurs most frequently.

median is the "middle" term. Arrange the terms in order in a line, and the median is the one in the middle of the line.

mean is the usual average. For the mean of n separate terms, add all the terms to get their sum, and then divide that sum by the number of terms (that is, divide by n). More exactly, that is the arithmetic mean.

For the geometric mean of n separate terms, multiply all the terms to get their product, and then take the nth root of that product.

All these will come to pretty much the same number if your data is distributed in the usual bell curve, but if it's not, the mean can paint a badly misleading picture of the data.