Minecraft wiki entry for summon, associated text: Java Edition:
To summon a charged creeper at the current position named "Powered Creeper":
summon creeper ~ ~ ~ {powered:1b,CustomName:'{"text":"Powered Creeper"}'}
NOTE: CustomName is a raw JSON text.
To summon a spider jockey:
summon spider ~ ~ ~ {Passengers:[{id:"minecraft:skeleton",HandItems:[{id:"minecraft:bow",Count:1b}]}]}
To summon a villager that trades 1 dirt block in exchange for 1 diamond:
summon villager ~ ~ ~ {Offers:{Recipes:[{buy:{id:dirt,Count:1},sell:{id:diamond,Count:1},rewardExp:false}]}}
Bedrock Edition:
To summon a patrol captain pillager at the current position:
summon pillager ~ ~ ~ minecraft:promote_to_patrol_captain
To summon a dolphin with the name "Dolphin" in a golden color:
summon dolphin §6Dolphin ~ ~ ~
To summon a red dyable wolf:
summon wolf ~ ~ ~ minecraft:on_tame