One major difference is that ecommerce warehouses have a lot of picking and sorting activities compared to B2B warehouses. B2B warehouses are to fulfill big orders (normally pallets) whereas ecommerce warehouses are used to fulfill small orders by the end consumers.

Another difference is that B2B warehouses' storage medium tends to be pallet racking or floor stacking. Ecommerce warehouse are inclined to shelving. Nowadays, automation such as conveyors and AGV can be installed and utilized.

I have walked pass some ecommerce depot. There were a lot of small vehicles parking and waiting. Is this the same for B2B warehouses?

Not really. B2B warehouses normally move the inventory in and out by pallets. So you will be looking at trucks and containers.

Incoming inventory most likely are from airports, sea ports and manufacturing plants. Outgoing can be to various locations such as wholesalers.

B2B warehouse means consult with retailers. and B2C means directly sale your items to customers.