What is Tax Loss Harvesting? How to save taxes using losses

Hello,
If we invest in MF through SIP monthly 10K (or yearly 1.2L) for say 12 years for some long-term perspective which is happening after 20-22 years from now. Then would tax-loss or tax-profit harvesting make any sense/useful (assuming the fund is not outperforming etc. or we are not bothering/comparing its performance etc. with others)?
(Note: Read this article to know about tax harvesting: Tax Loss Harvesting: How to Save Tax by Tax Harvesting)
To add more details to my question, in other words: If after 2-3 years the investment of say 2.5L becomes 3.4L then booking profits of 90K being tax-free and reinvesting it on the same day (just suppose) the entire 3.4L and repeating the same process after every 1-2 years for 10 years and then during 20th-22th years the final redemption(s) then would this process of booking profits to take benefit of LTCG (tax-free up to 1 Lakh) make any difference/impact (as every time we are reinvesting entire funds and goal is to keep invested for long term)?
Thanks.