It depends on the switch.
Some have a special port which either takes an standard ethernet cable, proprietary cable or one of a few other standard types between the switches.
Others just use a regular port and link through ethernet, and the software keeps track of managing them as a stack.
A Cisco 6224P switch stacking interface
A switch being stackable doesn't always mean the same feature set - so you need to look closely at what features stacking gets you when comparing different models and brands. For some, a stack is just a set of switches managed together from one IP address. For others it means a dedicated high speed connection between switches with various types of failover and redundancy.
Or you might not need stacking at all
If you are not concerned about managing the switches as a single unit (or they are in fact unmanaged switches to begin with), and don't need extremely high speeds (2-10gbit+) between the switches, and aren't looking to setup any sort of redundant switching - then you don't need stacking at all. You just chain one switch to the next with a regular ethernet cable (or a cross over cable, but if you still have a switch that doesn't do automatic cross over, you really should upgrade!).
The limitation here is that all traffic that travels between the switches is limited by that single link, probably at 100mbit/s or 1gbit/s. Whether or not that is a problem depends on your network design and needs. You also have to be careful to make sure you don't create loops between the switches, or have Spanning Tree Protocol enabled on all switches to prevent loops.
About the netgear smart switch and similar designs
The SFP ports are not necessarily for stacking or chaining switches - you can use the regular ethernet ports to chain switches together.
What the SFP ports give you is the option to use fibre optic cable instead of ethernet. This requires an SFP at each end. You would use fibre in cases where:
- The run needs to be longer than 100m - such as between buildings. Fibre can be configured to run for kilometers without any issues
- the run will be going through areas with heavy electrical interference where copper may not work