Jackie would that be correct foamy and bubbly?
Yes foamy and bubbly indicates an active starter. You can also use the float test as discussed in the Tartine book. Take a bit of starter and drop it into a bowl of water. If it floats or as soon as it floats, it's ready to use. If it sinks then give it more time. At the point that the starter starts to float, it's a young starter. If you allow the starter to sit and get even more active it will continue to float for a good while developing more acids. As the starter rises after being fed, it will continue to rise and then top off or dome. At the point that the starter starts to recede in the middle, it is at full maturity. A young starter vs a mature starter will give different results in texture and taste. Once the starter starts receding, then it is overmaturing. I try to look at starters as though it is another piece of dough. As it ferments, it will get bigger, reach it's peak and then become deflated.
As a fun exercise next time you go to feed your starter, instead of dumping the excess starter down the drain, leave it in a small bowl to watch it ferment. I also will taste a small bit of it with the tip of my tongue when the starter is young versus mature. You can definitely taste the difference in the acid load. These acids will contribute to the textural and taste differences so you can decide at what point you want to use the starter to get the desired end texture and taste.