What is Vitarka? What is Vicāra?

Vitarka (initial application) is searching without a specific target, like shining a flashlight around everywhere — the movement is obvious and rapid. Vicāra (sustained examination) is when, after searching around, one has found a rough target, and so attention is focused on the target for observation — the movement is light and slow.

When investigating Chan, after one has found a general direction and focal point for one's investigation, one begins to lock onto a target and observe and examine it, and the mind becomes even more subtle and dense, making it hard to detect.