what is the meaning of number 1e5?

this is scientific notation for 10^5 = 100000

1e5 means 1 × 10⁵.
Similarly, 12.34e-9 means 12.34 × 10⁻⁹.
Generally, AeB means A × 10^B.

1e5 is a number expressed using scientific notation and it means 1 multiplied by 10 to the 5th power (the e meaning 'exponent')

so 1e5 equals 1*100000and is equal to 100000, the three notations are interchangeable meaning the same.