The answer to 'difference between water heater installation' is that there are two main options: a standard tank-style water heater or a tankless (on-demand) water heater. Tank-style heaters store a large volume of hot water in an insulated tank, while tankless models heat water instantly as it's needed, without storing any. Both have their own benefits and tradeoffs in terms of cost, energy efficiency, space requirements, and hot water availability.
For most homes, a tank-style water heater is the more affordable and straightforward option to install. They are generally less expensive upfront and can be a good choice for homes with moderate hot water needs. Tankless heaters tend to cost more initially, but can save on energy costs in the long run and provide an endless supply of hot water on demand. They are a better fit for homes with high hot water usage or limited space for a large storage tank.