What ≥ means
The sign ≥ reads "is greater than or equal to". It is true when the left side is bigger than the right side or exactly the same: 7 ≥ 5 and 5 ≥ 5 are both true, while 4 ≥ 5 is false. Without the bar, the greater than symbol > is strict and leaves equality out.
In everyday language, ≥ means at least, no less than or minimum. A sign that says "Age ≥ 18" lets in 18-year-olds, not just people older than 18. On a number line, x ≥ 3 gets a filled circle at 3, and in interval notation it becomes [3, ∞).
The opposite statement is not ≤. If x ≥ 3 is false, then x < 3. Mixing these up is one of the most common slips in algebra.
How to type ≥ on any keyboard
On a Mac, press Option + . (period). On Windows, hold Alt and type 242 on the number pad. In Microsoft Word, type 2265 and press Alt + X. In Google Docs, open Insert > Special characters and search for "greater".
On iPhone and Android, the default keyboards have > but not ≥. Copy it here once, then save a text shortcut (on iPhone: Settings > General > Keyboard > Text Replacement) so a short word like "gte" turns into ≥.
In LaTeX, use \geq or \ge. In HTML, write ≥. In Excel, Google Sheets and most programming languages, type >= instead, because ≥ is not a valid operator there.
≥ vs ⩾ vs ≧
All three mean the same thing. ≥ is the standard form, ⩾ (\geqslant in LaTeX with the amssymb package) has a slanted lower bar that some textbooks prefer, and ≧ has a double bar. ≧ and its partner ≦ are also popular in kaomoji such as (≧▽≦).
Do not confuse them with ≳, which means "greater than or approximately equal to". The mirror-image sign is on the less than or equal to page.