If your current PC has a mechanical hard drive (HDD) you can upgrade to a solid state drive (SSD) for much improved performance.
Mechanical hard drives have moving parts, SSDs have no moving parts. They use less power and make no noise. For laptops this can lead to a noticeable improvement to battery life.
With a SSD you will notice that startup times will be reduced and programs will operate faster. The time lag or 'hang time' will be much reduced or eliminated altogether.
All hard drives deteriorate over time so if you need to replace your hard drive it makes sense to replace it with a SSD. The average lifespan of a hard drive is 3-5 years. Performance will reduce over time and ultimately the drive will fail. This will almost certainly mean data loss and operating system failure.
The price of SSDs has continued to fall making them relatively more affordable versus the old style hard drives.
For most users the operating system (Windows / MacOS / Linux) will need around 10-20 GB of space. Additional space will then be required for programs and personal files - photos, music, documents etc. Personal files can also be stored on external hard drives if you have a lot of personal data.
If I upgrade your hard drive to a SSD I will:
Backup the data on your current hard drive using specialist software.
Clone the data on your current hard drive to the SSD.
Install the SSD and check your system is working normally.