Net worth is everything you own minus everything you owe. It is the only personal finance number that cannot be gamed by moving money between accounts, which is why it is the one worth tracking monthly.
The direction matters far more than the level. A negative net worth in your twenties with a rising trend is a healthier position than a flat positive one in your forties.
Cash, investments, retirement accounts, property and anything you could realistically sell. Depreciating possessions are usually left out unless they are worth enough to matter, because listing a car at purchase price flatters the number and hides the trend.
Include the market value as an asset and the outstanding mortgage as a liability, so only the equity shows up. Some people track a second figure that excludes property entirely, since a house you live in cannot fund your retirement without you moving out.
Age based benchmarks are averages skewed by a small number of very wealthy households, so the median is far lower than the average and comparing to either tells you little. A more useful test is your net worth divided by your annual spending, which is the same figure as your years of freedom.
Monthly is enough. Daily tracking mostly measures market noise and tends to make people trade when they should not.