What ≤ means
The sign ≤ reads "is less than or equal to". x ≤ 10 is true for 10 and for every number below it. In plain English that is at most, no more than, up to or maximum: a bag limit of ≤ 7 kg allows exactly 7 kg.
Double inequalities use it on both sides. In probability, 0 ≤ p ≤ 1 says a probability lies between 0 and 1, both ends included. On a number line that means filled circles at both ends; in interval notation it is [0, 1].
Watch the opposite: if x ≤ 5 is false, then x > 5, not x ≥ 5.
How to type ≤
On a Mac, press Option + , (comma). On Windows, hold Alt and type 243 on the number pad. In Microsoft Word, type 2264 and press Alt + X. In Google Docs, use Insert > Special characters and search for "less".
Phone keyboards only have <, so copy ≤ from this page or set up a text replacement shortcut. In LaTeX, use \leq or \le, or \leqslant (amssymb) for the slanted ⩽. In HTML, write ≤. In Excel and programming languages, type <=.
≤ vs < and other look-alikes
< is strict: 5 < 5 is false, while 5 ≤ 5 is true. Read more on the less than symbol page. ⩽ and ≦ mean the same as ≤ and are just different styles. ≲ means "less than or approximately equal to", and ≪ means "much less than".
In most programming languages, <= is the comparison operator. Some coding fonts with ligatures draw it as one joined glyph that looks like ≤, but the file still contains two characters.
The reverse sign lives on the greater than or equal to page, and the whole family is collected under inequality symbols.