Can you explain "tax-loss harvesting" ?

[Hobohob]

I read the following advice in the newspaper’s financial section.
But I’m not sure what it’s telling me to do or avoid exactly.
Can somebody put it differently?

One thing investors can do to take advantage of the market’s big drop - without missing a big upturn - is what’s known as tax-loss harvesting.

This involves selling stocks or mutual funds in which you have a loss and buying a very similar stock or fund for at least 30 days. The sale generates a loss that reduces your taxes, within limits. However, the proceeds cannot be invested in substantially the same security within 30 days or it will be deemed a wash sale, and you will forfeit the tax loss.

After 30 days, you can sell the replacement stock or fund and reinvest the proceeds in the original security.

[CookingWithGas]

This is a way to declare a loss on a holding, then 30 days later buying it again. During the interim you buy something else that will perform similarly to the original holding.

The main reason you would want to realize a loss is if you have gains during the same period. The loss allows you to offset the gains for tax purposes.

Buying other holdings in the interim allows you to take advantage of any gains that might occur during that time, then you make a repurchase so you end up as if you had never sold the stock in the first place.

You have to wait 30 days because if you sell stock then buy the same stock within 30 days, the IRS won’t let you take the loss; they call it a “wash sale” which means even though there is a transaction on the books, the transaction was a sham just for tax purposes and doesn’t count as far as taxes are concerned.