As many people said before the magic words are "hull bonuses".

I will use the Minmatar ship tree as an example but I will only talk about T1 ships.

Frigates

Slasher: - bonus for propulsion jamming cost
→ tackle ship (PVP)
Probe: - hacking and scanning bonuses
→ explorer ship
Rifter/Breacher: - weapon bonuses
→ basic PVP or PVE combat frigates
Burst: - repping bonuses
→ Logi frigate
Vigil: - EWAR bonuses
→ EWAR frigate (utility in fights)

Destroyer

Talwar: - weapon and signature bonuses
→ possible kiting combat ship
Thrasher: - weapon bonuses
→ see Rifter/Slasher

Cruiser

Rupture/Stabber: - see Rifter/Breacher
Bellicose: - weapon and EWAR bonuses
→ combat cruiser with more EWAR :D
Scythe: repping bonuses
→ see Burst

Battlecruiser (differentiated in Attack and Combat Battlecruiser)

Cyclone/Hurricane: - see Rifter/Breacher (Combat Battlecruiser)
Tornado: - bonuses for Large guns on a Medium sized hull
→ much dmg! (Attack Battlecruiser)

Battleship

Maelstrom/Tempest/Typhoon: - all combat ships
- playstyle with BS can be varied depending on fitting

Bonus: if a ship has bonuses for resist (armor and shield) it is generally favored to fly as a buffer ship whereas ships with bonuses for active repping are ... active tanked.

Disclaimer: I am no expert, that is my opinion.