The Vineyard Explorer hosts all of your fruit sources, both vineyards that you manage yourself and those you source from. This is what the system references when you're adding a fruit, juice, or wine lot to the system.
The system tracks acreage, estimated yield, and cost per ton or acre for each block in each vineyard. Over time, as you source fruit from these vineyards across vintages, you'll be able to compare data on yields and fruit costs that will help you to make more informed decisions.
If you're looking to track harvest metrics (ie. Brix, TA, pH) in the vineyard you need to add a fruit lot that sources from that vineyard block. Then, record analysis on that fruit lot. That way it's specific to the vintage.