Set the background colour of every other row in a table to something other than the default colour, such as light grey and white.
If your table is quite heavy, or has a lot of information, using lines as dividers between rows can make it hard to read through or look at. Zebra striping makes the separation of rows clear, but isn't as visually heavy or distracting as solid lines.
It's best to start with the first row in a lighter colour. In many tables, the header row which has the column names is darker than the data rows. If your first row is the darker of the two colours used for zebra striping, it could be mistaken for a header row, or look strange next to a header row that's even darker.