Ranging is the opposite of trending, where instead of there being a clear direction the price of an asset is moving (either up or down), ranging means the price is sticking to a narrow band of prices between support and resistance levels.

For example, the price of BTC may range between $7000 and $6000 for weeks at a time. Showing no signs of either a upward or a downtrend during that period. Bitcoin would be said to be "ranging."

Trading within this range, where one goes long (buys) near $6000 and sells near $7000, and then shorts from $7000 to $6000, and repeat, is called "range trading." When done right it, with ample leverage, it can be extremely profitable.

When the price of an asset finally leaves this range, it's called a "breakout."