what is the difference?
Ok.
Law Clerk
A law clerk is often at the bottom rung. You will run to court and file. You will tabulate folders and maybe even answer phones. You might be asked to do some legal stuff like researching. You might be asked to do deliveries - basically, an office allrounder who might do some legal work.
Some people also use "clerk" when referring to summer clerks - these are the people who are normally 4th yr law students who spend a summer working at a larger law firm, gaining experience. This is how most law firms recruit grads.
Paralegal
Some law firms refer to the students who work there as paralegals - hence the confusion. The roles are often the same.
However - one important distinction is that some people are career paralegals. That means that they are not qualified lawyers - they can be people who started as secretaries or have done some legal subjects/courses at a college or TAFE - but have gained enough expertise with that field of law to actually do some of the paperwork involved in a matter.
So a conveyancing paralegal will work under a lawyer - but will do more than just take calls and read NW. They will order searches, converse with other lawyers, get instructions from clients, and so on - the nitty gritty.
So in a nutshell - law clerks - young students; paralegals can refer to older, more experienced people who do quite law-focused work (don't call them law clerks - it's be disprespectful)