Hi Robin, welcome!
"slip, slip, knit" is usually a decrease. "Slip" means move one stitch from your left needle to right needle without actually knitting it. In this case, put your right needle into the stitch as though you would knit it, but don't knit it, just move it over to the other needle. Do this twice, then you'll put both of those stitches back onto your left needle and knit them together with your right needle. The point of all that maneuvering is that it turns the stitches around so that your decrease leans to the right, instead of to the left. If you just knit them together (k2tog) without slipping them first, it would lean to the left.
The "slip 2 stitches individually purlwise" bit doesn't really make sense to me- are you sure you typed that out right? It means to move the stitches over to your right needle like you did before, but this time grabbing them as though you were going to purl. That moves them over without turning them around. PSSO (pass slipped stitch over) is another decrease where you slip one stitch, knit or purl the next, then "bind off" the slipped stitch by passing it over the knit or purled one. But the line as you typed it doesn't make sense to me. Hopefully someone more experience will be able to help you with that if it's typed correctly.
The next underlined part is an increase- you're making 3 stitches out of one. Knit the stitch, but don't drop it off your left needle. Do a yarn over, then knit the same stitch again, then drop it off your left needle and continue on.
OK, row 1 you knit one, slip one (move it to your right needle without actually knitting it