What is the Difference Between a Type-1 and a Type-2 Superconductor? As the title says, I was wondering what the difference was between a Type-1 and a Type-2 Superconductor. Especially in terms of the Coherent Length and Penetration Depth of a Magnetic Field - and how their relative sizes affect whether a Superconductor is Type-1 or Type-2.
 A: Introduction:
Superconductivity is phenomenon when certain materials electrical resistance drops sharply to zero when their temperature is lowered below it's critical temperature ($T_c$), There are two types of superconductors  $\mathrm{Type\text{ }I}$ and $\mathrm{Type\text{ }II}$. 
Type I Superconductors:
In $\mathrm{Type\text{ }I}$ superconductors transition from normal state to superconducting state occurs instantly i.e. at exactly it's critical/transition temperature $T_c$:

also this type of superconductors "repel" magnetic field lines fully, i.e. no magnetic field line could penetrate through in this type of superconductors:

As you can see no magnetic field line penetrates though this type of superconductor
Type II Superconductors:
In $\mathrm{Type\text{ }II}$ superconductors transition from a normal state to a superconducting state occurs "slowly" i.e. as you decrease temperature from it's critical temperature superconducting properties increase:

As you can see on image, there is small curve which approaches zero resistance after critical temperature $T_c$. The Common and most popular example of Type II superconductor is YBCO superconductor, which critical temperature is $90K$.
Also some magnetic field lines can penetrate though in this type of superconductors allowing Flux Pinning which is also know as Quantum Locking:

As you can see on image, some magnetic field lines can penetrate though this type of superconductors, thus resulting aforementioned Flux pinning. Using this it is possible to say that this type of superconductors aren't ideal superconductors.
Conclusion:
So there are few differences between Type I and Type II superconductors, first of them it transition of superconducting state, second is magnetic field lines. Also there are few more differences between them, for example Type I superconductors always have lower critical temperature than the most of Type II superconductors, also There is theory (BCS Theory) which explains only type I superconductors but can't explain type II superconductors (i.e. High temperature superconductivity)
