Bootstrap is no similar to branch length. 

The bootstrap value represents the indicator of good or poor support in phylogenetic tree.

Bootstrapping is a resampling of alignment sequence multiple (ASM) analysis by replacing characters out of your analysis, then rebuilding the tree. This step can be realized n iterations which resulting n phylogenetic trees. Finally, all n phylogenetic trees are tested if the same nodes are recovered. This is done through many iterations, n can be 100 or 1000. More details see [1].

[1] Soltis, P.S. and Soltis, D.E., 2003. Applying the bootstrap in phylogeny reconstruction. Statistical Science, 18(2), pp.256-267. 

I hope that helps. 

Nadia Tahiri

Thanks so much Nadia. The article is really easy to understand.

I also got this answer from a colleague: 

Bootstrap values and branch length are different.

Bootstrap values are those shown on the branch nodes or joints, these indicate a percentage reliability of your computations.

Branch length measures the distance between each strain from the original point and the branch nodes. The shorter the branch length is, the more closely related the strains are and vice versa.

Cheers

Thanks, James, for developing the concept of branch length. it would be more clear. 

Cheers,

NT