You can create more complex search criteria using "Nested Searches". As an example, if you wanted a rule to match when the subject contains "Product" or "Service" and also require that the sender is either "Bill" or "Bob" then you can use nested searches.
eg. (Subject contains "Product" or "Service") and (From contains "Bill" or "Bob")

Tap on the "+" button below the Search section to add a search. Choose "Nested search" from the top of search choice screen. This will open a new screen with the new nested search. In this example, tap on the Search "+" button to add "Subject" - "Contains". In the text field, type Product (no quote " characters)
Repeat the same steps to add another search field for "Service". Check that the comparison is "or" between the fields. Tap on "and" to change to "or".

Go back to the previous screen. Tap on the Search "+" button and choose "Nested Search" again. In the new nested search screen, tap on the Search "+" button and choose "From" - "Contains". In the text field, type Bill (no quote " characters)
Repeat the same steps to add another search field for "Bob". Check that the comparison is "or" between the fields.

Go back to the previous screen and you will now see the nested searches in the Search section. Check that the comparison is "and" between the nested search. Tap on "or" to change to "and".
If you want to try this example yourself, copy the text below and then tap on the action menu in the top of a search/rule screen, then choose "Paste filter fields"

and (
  or (
    Subject Contains Product
    Subject Contains Service
  )
  or (
    From Contains Bill
    From Contains Bob
  )
)