nslookup — Quick Domain Name Lookups
nslookup answers the simplest DNS question there is: what does this name point at? It is the tool most people reach for first because it requires no flags to be useful — give it a hostname and it returns the address, give it a record type and it returns those records. It is less detailed than dig and that is precisely why it is useful: when you need a quick, unambiguous answer rather than a full protocol-level dump, the shorter output is the point.
Why run it
The everyday case is verification after a change. You have updated a record at your registrar, or pointed a subdomain at a new load balancer, and you want to know whether the change is live. It is also the first thing to run when a service is unreachable, because it separates the two biggest categories of failure immediately: if the name does not resolve, the problem is DNS and nothing downstream matters yet; if it resolves to an address you do not recognise, the problem is that it resolves to the wrong place, which is a different and often more alarming situation.
Why automate it
Nobody re-runs a lookup for a name that is currently working, which is exactly the gap automation fills. A scheduled lookup notices the day a hostname starts resolving somewhere new — an expired lease reassigned to someone else, a failover that fired and never failed back, a staging record accidentally promoted. Because the check is cheap, it can run against every name you own rather than the handful you remember to check, and that breadth is where the value is: the record that breaks is almost never the one you were watching.
What it gives you
A fast, unambiguous answer to "where does this name point?", available for every name you are responsible for rather than the few you check by hand. Run once it resolves an argument; run continuously it tells you the moment an answer changes.