Halimar Tidecaller in card text it says Land creatures you control have flying. Does this mean any creature without flying or does it mean a land which is also a creature
A permanent which is both a land and a creature.
Let's together find out what they exactly mean with 'land creatures'. In the Comprehensive Rules we find the following regarding multiple card type:
205.2b Some objects have more than one card type (for example, an artifact creature). Such objects satisfy the criteria for any effect that applies to any of their card types.
Meaning that in this example the object benefit from being an artifact as well as a creature. But on the flip side..
300.2. Some objects have more than one card type (for example, an artifact creature). Such objects combine the aspects of each of those card types, and are subject to spells and abilities that affect either or all of those card types
So they are also approachable by all the types the card currently has.
But we want to know what cards are being affected by Halimar Tidecaller static ability ("Land creatures you control have flying."). Does that mean all lands or all creatures or all lands that are also creatures?
It says on the card 'Land creatures you control' which indicate that any object that satisfy that criteria is affected. So not just lands or not just creatures, but only 'land creatures'.
Although neither previous answer is wrong, I feel that the first sentence in both is a little misleading. My version:
It is a permanent which is both a land and a creature.
The distinction is that it's not more true to say "it is a land which is also a creature" than it is to say "it is a creature which is also a land".
The simplest example is the card Dryad Arbor. This is a card that has both the type "land" and the type "creature", which means that it has all the properties of both.
As others have pointed out, other common ways to have an object be both a land and a creature is the Awaken mechanic and "man lands" that can become creatures.
A regular creature can also become a land creature, through things such as Life and Limb.
It means lands which are also creatures.
Halimar Tidecaller is from the Battle for Zendikar block. Both the original Zendikar block, and the newer Battle for Zendikar block, have a sort of low-scale theme for land creatures, having many spells and effects which turn lands into land creatures. Pointed examples include the "manlands" and the Awaken mechanic.
Halimar Tidecaller is describing permanents you control with the "land" and "creature" qualities, just like Paragon of Gathering Mists is describing permanents you control with the "blue" and "creature" qualities. If they meant creatures without flying they would have used the "creatures without flying" phrase.
You might notice Halimar Tidecaller also gives you back a "card with awaken". That's referencing the Awaken mechanic. Halimar Tidecaller is made mainly for decks that care about using that mechanic, and want to re-use spells that have it.
The short answer is it is an object on the battlefield that is both a land and a creature at the same time.
Halimar Tidecaller was printed in the same set as cards with the ability awaken, for example Ruinous Path. These cards had an alternate cost that would do the main effect and also awaken one of your lands as a creature, that land would still be a land, making it into a land creature.
This is not the first time there have been cards that were both land and creature, Dryad Arbor is probably the most notable example, being the only card that was printed as both, but many cards like Mutavault are lands which have an ability to temporarily turn them into creatures. There are also some enchantments that do this, such as the 6 Genju cards of Kamigawa Genju of the Realm and the 5 Zendikon of Zendikar Wind Zendikon. Life and Limb combines saprolings and forests, making them all land creatures. Finally there are planeswalkers that make lands into creatures like Koth of the Hammer.