All positive and negative integers, fractions, and decimal numbers; technically, any number that can be expressed as a fraction of two integers - which means everything except numbers containing weird radicals such as (pi) or e or square root of 2.
Any number that does not end or repeat (in other words, any number that isn't rational). This includes all numbers with radicals that can't be simplified, such as square root. Also all numbers containing PI or E. Note that repeating decimals like 0.3333... are rational