Foundation Scholarships are provided by donors and can be tailored to specific types of students based on the preferences of the donors. For example, a foundation scholarship may be designed for female, first-generation nursing students from Houston County. You will not be eligible for all foundation scholarships, but you may be eligible for some. Look and apply!
Merit Scholarships are based on what you've earned academically. These are based on your GPA and your ACT/SAT score (unless your particular school is Test Optional).
Many schools allow scholarships to stack. This means you could earn a foundation or merit scholarship but also apply local scholarships and grants to your balance. This means you should apply for as many scholarships as you are eligible for.
While the dream is to have college tuition covered by scholarships rather through student loans, remember there may be benefits outside of the financial realm. As more prestigious universities do not often offer many scholarships, some students opt to attend a more prestigious university (via student loans) because of the reward of alumni status, hireability, and networking potential.
Some colleges accept an ACT Superscore, but not all. Not every university even accepts your Superscore for admission and scholarships. (Your Superscore is the composite of all your highest ACT subject tests.)