The front door is the most common entry point for burglars, closely followed by windows. Your windows are inherently vulnerable because glass is easier to break and people can gain easier access. Sometimes, windows need some additional protection and security.
If you are going to have some additional security features fitted to your windows, make sure they are appropriate for your property. For example, if you want to protect your home, think about retractable grilles, or perhaps bars that are not as intrusive or invasive. You could also think about alarms instead, which will sound when force hits the window, so if somebody was breaking in, then the alarms would go off. This means you will be protected in the event of somebody breaking into your home.
For a commercial building, you will probably need more protection, in the form of grilles or perhaps a security shutter. This will be harder to break into, offering you more protection.