Kaspersky has a few issues with Microsoft in the past, in the respect that the company insists on installing and defaulting Windows Defender as the primary choice of security suite for any new Windows 10 user. Although Windows Defender is a reasonable security suite in its own right, it's never going to win any security awards or trump a dedicated security suite.
Kaspersky Free will offer users basic anti-virus protection against the most common threats, such as malware, network attack and phishing. It also includes a free on-screen keyboard to prevent key loggers from intercepting your keyboard typing when you login to your online bank account.
Although Kaspersky Free is light on resources, this is also due to the fact that there are many missing modules you'd receive in the commercial suite, Kaspersky Internet Security. There's no firewall, safe money, no parental control, it's lacking a software cleaner, a system rescue disk, no network monitor and much more.
You do receive the Kaspersky Secure Connection feature, but this is limited to only 200MB/day which isn't ideal if you want to use the feature as a VPN whilst travelling abroad.
In addition, Kaspersky Free is only suitable as a single PC install for home users.
If you're a power user and only need the minimum protection, then this is the security for you.