What is the difference between these words for vegetables in Spanish?

legumbre,
vegetal,
verdura,
hortaliza.

My understanding is this: 

Hortaliza= all vegetables.

Verdura= salad vegetables.

Legumbre= legume in English, so that's peas, lentils and beans. But I've heard Spaniards refer to 'frutas y verduras' in the same way we say 'fruit and vegetables' in English.

Vegetal=plant but I've seen 'bocadillo vegetal' on a menu , but 'plant sandwich' sounds odd in English, so I wasn't sure if vegetal meant salad, or things like carrots!