Whatever of this gets too close to egg sucking lessons, please just ignore but I'll start from somewhere near the beginning.
b&w papers use a grading system to show contrast, with 5 being the highest. Grade 5 is very extreme and looks not too far from a photocopy without lots of attention to getting the exposure just right to tweak out any detail.
At the bottom of the scale (can't actually remember if it's 0 or 1 anymore) you get a very soft image with practically no hope in hell of getting a solid black anywhere in the print.
So, once you've decided what level of contrast you want, there are two ways of getting that grade. One is to choose a graded paper and print on that.
If you get a grade 3 paper, it will always be grade 3 no matter what you do with it. No filters or colour of light, or exposure changes will effect the contrast the paper gives at all.
The other way is to use multigrade paper. This responds differently to the colour of light the enlarger emits and you use this to set your contrast levels.
With a "b&w" enlarger, there is a little tray in the head that you place coloured gel filters into. They come in a box, usually going up in half levels.
If you have a colour enlarger then it will have 3 colour controls on it that allow you to choose the level of three colour filters that adjust the light falling onto the print through the neg.
These are Yellow, Magenta and Cyan. Various combinations of the yellow and magenta filters produce exactly the same colours as the contrast filters for b&w enlargers.
The combinations that you need will be listed on the box for multigrade papers and these are probably the best place to start as it allows you to experiment without buying lots of different papers of different grades.
Also with multigrade papers, you can have a soft print but burn in certain areas at a higher grade if you need little spots of higher contrast..... but perhaps we should save that for another day.
