Make One Purl (M1P) Increases
A Left-Leaning or Right-Leaning Single Increase
The 'Make One Purl' (M1P) is the purl row equivalent of the (more common) 'Make One' (M1) increase.
Both are single increases (i.e. they increase the overall number of stitches on your needles by 1), but the M1P is used on a row of purl stitches rather than on a row of knit stitches.
As with the M1, the M1P can be either right-leaning (M1pR) or left-leaning (M1pL).
It all depends how you want the increase to look on the front of your knitting.
However, as a beginner this is not something you should worry about, as a knitting pattern will usually tell you which one to use. And it it doesn't, then I would recommend choosing the M1pR because it's simply easier to do!
A big advantage of the M1P is that it doesn't create an obvious, raised pattern in your knitting; in fact, it's often referred to as an invisible increase.
Please find the video tutorial below:
I hope this has been helpful :)