Quick answer: US treble crochet is a tall stitch made with two yarn overs before insertion; in UK terminology the same construction is called double treble crochet.
Treble Crochet Steps
Yarn over twice, insert the hook into the next stitch, yarn over, and pull up a loop. Four loops should be on the hook. Yarn over and pull through two loops three times until one loop remains.
Treble Crochet Height
Treble crochet is taller and more open than double crochet. It creates drape quickly but needs steady loop height to prevent loose or distorted fabric.
Turning Chains and Row Edges
Follow the pattern's turning-chain count and whether that chain counts as a stitch. Mark the last real stitch and count before turning to prevent widening or narrowing edges.
US and UK Treble Crochet Terms
This page uses US terminology. US treble crochet corresponds to UK double treble crochet. UK treble crochet corresponds to US double crochet, so verify the pattern language before starting.
Fix Uneven Treble Stitches
Keep each yarn-over loop on the hook shaft at a similar height. Work the pull-through-two steps without tightening the lower loops, and check that all three pull-through stages are complete.
Use the instructions and terminology stated by the pattern you are following. Make a swatch when gauge or finished size matters.