Non-solid blocks is blocks which we only can hold with a container like buckets, glass bottles, let's see some non-solid blocks:
(ID 0) Air= Default minecraft air
(ID 8) Water Still= Moving Water
(ID 9) Water= Static Water
(ID 10) Lava Still= Moving Lava
(ID 11) Lava= Static Lava
(ID 90) Portal= A frame of Nether Portal
(ID 119) End Portal= A frame of End Portal