Let's say C:\Users\john.doe\Documents\example.txt contains the follow two lines.

Hello
World

Get-Content can be used to read the content of a file. In this example, both lines are returned.

> Get-Content -path C:\Users\john.doe\Documents\example.txt
Hello
World

Select-String can be used to filter the results.

> Get-Content -path C:\Users\john.doe\Documents\example.txt | Select-String hello
Hello

Notice in the prior example that Select-String is case insensitive by default. The -CaseSensitive flag can be used to perform a case sensitive filter.

> Get-Content -path C:\Users\john.doe\Documents\example.txt | Select-String -CaseSensitive Hello
Hello

The -Pattern option can be used to perform a regular expression search, such as finding lines that being or end with a certain string.

> Get-Content -path C:\Users\john.doe\Documents\example.txt | Select-String -Pattern ^Hello
Hello

And here is how you would search for two (or more) strings.

> Get-Content -path C:\Users\john.doe\Documents\example.txt | Select-String 'Hello|World'
Hello
World