Alkanes: These are saturated hydrocarbons with single bonds only. Like stacking wooden blocks directly on top of each other without any gaps.
Alkenes: These are unsaturated hydrocarbons containing at least one carbon-carbon double bond. Imagine if two sides of your wooden block were glued together - this is akin to a double bond.
Aromatic Hydrocarbons: These are hydrocarbons containing ring structures with alternating single and double bonds. Picture arranging your wooden blocks in a circle or ring pattern.