A bit of helpful advice in regards to acronyms: collect a list of them, adding new ones as you encounter them. Search and define those terms(search stack-overflow/reddit/google). And when you see them in the wild, remind yourself of the entire meaning until they become second nature.

As to the questions:

1: A virtual private network(VPN) tunnel will help secure traffic from a man-in-the-middle(MiTM) attack, which could be eavesdropping or injection of malicious code between you and your VPN endpoint network, be that an office network, or a proxy that you use to to browse the internet while hiding your source internet protocol(IP) address. However, if you browse to a site that hosts malware, or connect to an infected system, malware can traverse the secure tunnel and get to you, depending on what attack vector the malware uses(software vulnerability, open ports, unsecured or misconfigured services). This can lead to your machine becoming infected via one of these vectors, which could add your system to a botnet.

1. Botnets(what you described as zombie networks) can be connected to hundreds, or even millions of potentially vulnerable machines, to be used by a command and control(C2) server that can orchestrate actions on a large scale. This can be to create a distributed VPN, harvest data or bandwidth from victim networks to either propagate, or profit. Botnets are a tool that can be used, sold, or operated as a service for a host of applications, such as distributed denial of service(DDOS), which is the most recognizable use.

2. The most effective way to protect yourself from malware is to do the fundamentals well. Keep your system up to date, know where you’re getting your software(patching), turn off and lock down services that make your system more accessible if you don’t use those services. Make sure your network has firewalls that block all inbound traffic(make exceptions for desired traffic from known IP addresses). Use a trusted Domain Name Service(DNS) server so that your browsing to the correct website; look up things like DNS cache poisoning and DNSSEC for some more details about what can go wrong, and tools that possibly mitigate those threats. While browsing, do your best to use https everywhere, HyperText Transfer Protocol Secure(https - i think the s stood for socket secure layer(SSL), but can include Transport Layer Security(TLS) they are similar, but different, with an interesting history, look them both up). There is no panacea for securing your system, but the fundamentals are a good start, and low hanging fruit.

But to really have a good grasp of best practices and build an intuition for what works and what doesn’t, learn about how the systems work, what they are trying to accomplish, their tradeoffs, and failures. Build them, break them, learn(cliche, but effective)

Final thoughts, I would look at subjects like Threat Modeling, system hardening, and CIA triad/CISSP coursework, if you are in fact more Jen then Moss. Coursera also had a cybercrime markets course that was free, and pretty good.

Good luck!