There are many different batteries currently in production today worldwide.
Lead Acid Batteries can generally be described first by Type or Construction:
Sealed Valve regulated or Starved Electrolyte types use a solution of sulfuric acid and water suspended in a GEL or absorbed into a glass-mat (AGM). There is no excess electrolyte to leak out even if tipped or turned upside down. This sealed, non-spillable characteristic is a product of the construction and chemistry of the battery design.
Sealed Maintenance Free Flooded and Accessible Maintenance Free Flooded types use a solution of sulfuric acid and water that can spill out of the battery if it is tipped. Even though the Sealed Maintenance Free Flooded batteries are not accessible, electrolyte will eventually leak out through the vents if tipped.