The reason an engine throws a rod is usually due to revving the engine too high especially when the oil pressure hasn't built up enough such as right after starting the engine you rev the engine up.
That would cause the engine to not get enough lubrication in time so then the piston rods and rod bearings do not get enough lubrication from the oil.
Then the piston rod breaks and then throws the rod which causes the engine to seize and possibly cause engine damage.
Other causes of an engine throwing a rod are lack of oil pressure, bad or failing oil pump, low oil levels, not changing oil often enough etc.
When a vehicles engine throws a rod it typically requires tearing the engine completely down and rebuilding the engine.
So you may either need a complete engine rebuild or even a new engine.
Sometimes the car or vehicle may not be worth fixing or putting a new engine in if the value of the car is low.
But sometimes it may be worth the cost of putting a new or rebuilt engine in the car or truck or other vehicle.
To prevent a rod from throwing in an engine or prevent bearing failure in the engine make sure you have proper oil pressure, change the oil every 3,000 to 6,000 miles and also change the engine oil filter.