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What is bottom up Parsing ?
The Parsing method in which the Parse tree is constructed from the input language string begining from the leaves and going up to the root node.
Bottom-Up parsing is also called shift-reduce parsing due to it's implementation.
The YACC supports shift-reduce pasing.
e.g  Suppose there is a grammar G having a production E
               E->E*E
and an input string   x*y.
The left hand side of any production are called Handles. thus the handle for this example is E.
The shift action is simply pushing an input symbol on a stack. When the R.H.S of a production is matched the stack elements are popped and replaced by the corresponding Handle. This is the reduce action.
Thus in the above example , The parser shifts the input token 'x' onto the stack. Then again it shifts the token '*' on the top of the stack. Still the production is not satisfied so it shifts the next token 'y' too. Now the production E is matched so it pops all the three tokens from the stack and replaces it with the handle 'E'. Any action that is specified with the rule is carried out.
                                  If the input string reaches the end of file /line and no error has occurred then the parser executes the 'Accept' action signifing successfull completion of parsing. Otherwise it executes an 'Error' action.

What is a LR Parser ?
The LR means Left-to- Right signifying the parser which reads the input  string from left to right. An LR parser can be written for almost all Programming  constructs.
                      An LR parser consists of two parts:- Driver Routine & Parsing  Table. The Driver routine is same for all the Parsers ,only  the Parsing Table  changes. The Parsing Table is essentially a form of representing the State-  Transition Diagram for the language. It consists the entries for all possible  States  and the input symbols. In each state there in a predetermined next state  depending upon the input symbol. If there is any duplicate entry or two next  states for the same symbol, then there is an ambiguity in the grammar.

What is LALR Parser ?
LALR is Look-ahead LR parser. It differs from LR in the fact that it will look ahead one symbol in the input string before going for a reduce action. Look- ahead helps in knowing if the complete rule has been matched or not.
e.g Consider a grammar G with production
         P->AB|ABC
When the Parser shifts the Symbol B it can reduce to P . But if the next Symbol was C then it has not matched the complete rule. A LALR parser will shift one extra token and then take a decision to reduce or shift