Short answer: it is a freeware that claims to secure your online activities by preventing you from visiting malicious sites.
Personal Opinions: I have never installed this software but if ever I do, I prefer to do so through their official site only and never through offers in installation of another software, because this is most common cause of spreading of malware and spamming softwares.
Alternatives: I use Web of Trust (or WoT) chrome plugin that uses huge user base and advanced database to gather knowledge about malicious sites and prevents me from visiting such sites. It even shows whuch links on any given page are okay and which are harmful by displaying an icon. I can ignore it to download from a trusted site but if I download a malware, I have to use an antivirus to remove it.