Does it indicate the pure return of my investment combination on the
market or it includes the monthly deposit from my employer and my
deduction from my paycheck?
Contributions you make and employer matching are not included in the rate calculation. If they were then your rate of return would be much higher. Consider if you had $1000 in the account at the end of last year, and you put in $1000 this year and your total was currently $2000, you would have a 0% rate of return this year, not 100%!
Your personalized rate of return does not include your contributions, but it is affected by the timing of them. Typically contributions are made at every paycheck, which means most people will have somewhere between 12-52 contributions per year. But let's pretend you only had 1 or 2 contributions in a year in this simplified comparison:
- You make 1 contribution of $1000 at the beginning of the year. During the first 6 months your investments don't do very well and you get an average rate of -3%. (After 6 months your balance is $970.) During the 2nd 6 months of the year your investments do well and you get an average rate of return of 8%. (After 12 months your balance is $1047.60.) Your average rate of return for the entire year in this case is 4.76%.
- You contribute $500 at the beginning of the year, and $500 after 6 months, and the rate of returns are the same as above. After 6 months at -3% you would have $485, and after 6 more months of 8% you would have $1063.8, which yields an average rate of return of 6.38% for the year. You did better in this situation because you had less money invested during the losing period, so you lost less. This meant you had more to invest during the gaining period.
Note that the explanation you quoted mentions that fees (and credits) are included in the rate calculation, so your total rate could be slightly lower (or higher) than the aggregate of the individual investments in your portfolio.