Is about understanding LAMMPS input file

I am trying to run my MD calculations for the first time using LAMMPS impute script for a system of cellulose, polyethylene and cellulose+polyethylene. But I dont understad these command lines.
thermo: 100
timestep: 0.1
run: 1000000
I always ran into problems like segmentation error.
Is it the right way to go about it.
And I wanted to run for 50 picoseconds is there anyway I can go about it

Please check out the LAMMPS manual. There is a lot of information there. You probably want to start here: 5. Commands — LAMMPS documentation

Segmentation fault is a “secondary error” and usually the consequence of some other mistake. What to do depends on what process is having the segmentation error. Often it is the mpirun or mpiexec command segfaulting because the program aborted. Then you need to investigate where the error is coming from.

If you are a beginner with LAMMPS you should not be running something that is new, but rather start with something simpler like liquid argon and bulk water and experiment with those systems by changing input file settings to figure out what works and what doesn’t work. You should only start to set up and simulate a new system after you are familiar with how to reproduce correct results for simpler systems. Otherwise you will always have problems to tell what are the origin of problems with simulations failing to run or failing to produce meaningful results, since you cannot tell whether you made a wrong input, chose bad commands, made other technical errors or have genuinely unusual results.

In general, a lot of problems are avoided by getting proper tutoring on MD simulations in general (not necessary specific to LAMMPS), which is something that you cannot get from reading a manual or asking questions in a forum.

Thank you very much.
I really appreciate