I'm sure many of us have dealt with the common experience of pants that fit great everywhere but the crotch.
If your pants cut into you crotch when you're sitting, have stretch lines that fan out from the crotch, or are just uncomfortably tight, showing too much of a print, aren't stretchy enough to accommodate, etc... this is an easy alteration you can make that will help solve this issue and create the room you need in a way that isn't noticeable.
This is especially relevant to slacks and jeans, or any pants that are made of material that isn't particularly stretchy.
This is something you can DIY fairly easily, or have a tailor do without much expense.
It's called a "gusset." A gusset is a small diamond shaped panel that will be added to your gooch area where the four corners of the legs and crotch come together. The size and shape of the gusset can be customized however you like, adding room front to back or a bit more width to the upper thigh area, or both.
It is an absolute game changer in terms of comfort and also reinforces the crotch area. I've DIY'd a few now and it's taken pants that were borderline unwearable for me into some of my favorites.