Glossary
Plant
In one line: Planting the spike on a site: 4 seconds, then a 45 second timer starts.
What it means
On attack the goal is to plant the spike in one of a site's plant zones. It takes 4 seconds standing still; from then on the spike detonates after 45 seconds unless the defense defuses it. Planting also gives the whole attacking team 300 credits, even if you lose the round.
Where you plant matters: a spike visible from safe positions is easy to protect in the post-plant; a spike tucked behind cover forces whoever guards it to expose themselves. Before planting, someone must cover the planter.
An example
Three of you take the site. You plant where it can be seen from the two spots your teammates will play afterwards. Four seconds and the spike is down: now the defense has to come and get it under your fire.