A starter is flour and water that grows yeast and bacteria. The flour acts as food to the yeast. In order to grow, yeast needs to food. Yeast is most active in warmer temperatures (until about 110F). This means that cooling down your starter (i.e. putting your starter in the fridge) slows the growth.
Feeding your starter:
- Discard about half to three quarters of your starter. You can use this in cooking - pancakes, biscuits, etc if you wish, or just toss it. (the only reason you "discard" the starter, is so it doesn't keep growing bigger and bigger)
- Feed your starter the following (if you have a kitchen scale, use equivalent amounts flour & water):
- 1/4 cup flour (I do half bread flour, half whole wheat flour)
- 2 tablespoons water (should be at room temperature)
- Mix until well incorporated
Storing your starter:
If you keep your starter at room temperature, you should feed it every 12 - 24 hours. I feed mine every night. The advantage of feeding your starter daily is that you can use it in cooking - breads, biscuits, pancakes, etc. whenever you want.
If you plan to use your starter less frequently (once a week or less) - you can keep it in the fridge. When keeping your starter in the fridge, you should feed it every 1 - 2 weeks. The advantage is less maintenance. The disadvantage is that for many sourdough recipes, you will need to have planned ahead. As an example, if I kept my starter in the fridge and wanted to make bread on Sunday - I would probably take my starter out of the fridge Saturday morning and feed it. Then I would feed it Saturday night once more. And then Sunday morning it would be ready to use in cooking. Feeding it a few times before hand allows the yeast to become active and strong and give a good levain to the bread.
Starters are pretty strong, and a lot of times when people think they've "killed" they're starter, it can often be revived.
I hope this is a good intro. Reach out if you have any questions! Good luck!