The hiragana 「は」 is pronounced as "wa" when it's used as the particle which translates about as "As for (the preceding word/phrase)", but is otherwise pronounced as "ha"; this hiragana is useldy the used when using roumaji, even when it's still spelled as "ha" it's pronounced as "wa".
The hiragana 「は」 is pronounced as "wa" when it's used as the particle which translates roughly as "As for (the preceding word/phrase)", but is otherwise pronounced as "ha". To indicate that this is the hiragana being used, when using roumaji, it's still spelled as "ha" even when it's pronounced as "wa".