What Did Trent Mean By “Tithes?”

The Council of Trent did require all who were legally obligated to pay tithes to do so and also required all who collected the tithes to turn them over, in full, to the proper church. All who interfered with this practice were condemned.

You are correct that this would have been ten percent. It could have been ten percent or money or land, depending upon the custom and laws of the particular region.

The Church no longer requires anyone to give ten percent of income. The Church simply asks Catholics to support the mission of their parish (canon 222). This can be monetarily or through a donation of time and talent.